1. Technical Field
The present invention relates to a light-emitting device and an electronic apparatus.
2. Related Art
In recent years, electroluminescent (EL) devices including EL elements which are self-luminous and which serve as pixels have been being developed. Japanese Unexamined Patent Application Publication No. 2003-114626 (hereinafter referred to as Patent Document 1) discloses a light-emitting element for light-emitting devices. The light-emitting element includes an insulating layer; thin-film transistors (TFTs) arranged on the insulating layer; an interlayer insulating layer which is made of an organic resin and which lies over the TFTs; and a light-emitting layer which is sandwiched between a pair of electrodes, which is disposed above the interlayer insulating layer, and which contains an organic compound.
Patent Document 1 describes that the organic resin is moisture-permeable and absorbs water and the organic compound, which may have low or high molecular weight, is disadvantageous in being extremely susceptible to oxygen and moisture and therefore is readily deteriorated. An anode or cathode included in the light-emitting element contains an alkali metal or an alkaline-earth metal, which are readily oxidized by oxygen. That is, water or moisture degrades the light-emitting element to cause defects such as dark spots.
Patent Document 1 also discloses a light-emitting device including an insulating layer, a light-emitting element, and an inorganic insulating layer principally containing silicon and nitrogen or a carbon layer which has sp3 bonds and which contains hydrogen, the inorganic insulating or carbon layer being disposed between the insulating layer and the light-emitting element.
The light-emitting device disclosed in Patent Document 1 is a bottom emission type of organic EL device in which light emitted from a light-emitting layer is extracted through an element substrate. On the other hand, a top emission type of organic EL device in which light is extracted from the side opposite to an element substrate has been recently being developed.
FIG. 8A is a plan view of a conventional light-emitting device. FIG. 8B is a sectional view of the conventional light-emitting device taken along the line VIIIB-VIIIB of FIG. 8A. FIG. 9 is a sectional view of the conventional light-emitting device taken along the line IX-IX of FIG. 8A. The conventional light-emitting device is a top emission type of organic EL device. With reference to FIG. 8B, the conventional light-emitting device includes an element substrate 2 and reflective layers 27 arranged thereabove. An inorganic insulating layer 25 similar to that disclosed in Patent Document 1 lies between the reflective layers 27 and pixel electrodes 23.
Light emitted from the light-emitting layer 60 has a broad spectrum and is not bright. Therefore, a display unit including the light-emitting device has a problem that sufficient color reproducibility cannot be achieved. Japanese Patent No. 2797883 (hereinafter referred to as Patent Document 2) discloses an organic EL device having optical resonant structures. In the organic EL device, light emitted from a light-emitting layer travels between reflective layers 27 and a common electrode 50. A portion of the light that has a resonant wavelength corresponding to the optical distance therebetween is extracted in an amplified manner. The extracted light portion is very bright and has a sharp spectrum. When light-emitting elements include respective pixel electrodes 23 having different thicknesses, that is, when the optical distances between the common electrode 50 and the reflective layers 27 are different, from each other, lights having wavelengths corresponding to red, green, and blue can be extracted.
In the conventional light-emitting device, as shown in FIG. 8A, a crack 90 is initiated at a corner of one of the reflective layers 27 to propagate along end portions of this reflective layer 27 in some cases. With reference to FIG. 9, the crack 90 propagates through the inorganic insulating layer 25 and one of the pixel electrodes 23. The crack 90 is probably caused because the following stresses are concentrated on the end portions of this reflective layer 27: residual stresses created during the formation of an organic insulating layer 284, the reflective layers 27, the inorganic insulating layer 25, and the pixel electrodes 23; thermal stresses caused by differences in thermal expansion between these layers and electrodes; and other stresses. The presence of the crack 90 propagating through the inorganic insulating layer 25 and this pixel electrode 23 allows moisture contained in the organic insulating layer 284 to be diffused into an organic EL light-emitting element 3. This causes a problem that defects called dark spots arise.
In the above organic EL device, when the pixel electrodes 23 have different thicknesses such that optical resonant conditions are satisfied, the dark spots are frequently formed in blue light-emitting elements 3B included in the organic EL device. This is probably because the pixel electrodes 23 included in the blue light-emitting elements have the smallest thickness and therefore have the lowest cracking resistance,
In order to satisfy the optical resonant conditions, an inorganic insulating layer included in the organic EL device needs to have an extremely small thickness. Hence, it is difficult to prevent the formation of cracks by increasing the thickness of the inorganic insulating layer.